In Björn Hof et al.: Eliminating turbulence in spatially intermittent flows, Science 19, March 2010: Vol. 327, No. 5972, pp. 1491-1494, which in its entirety is incorporated herein by reference, the inventor of the present invention and co-authors disclosed a method of eliminating turbulence in a spatially intermittent flow through a pipe in that the parabolic velocity profile of a laminar flow is distorted to a plug like velocity profile upstream of a turbulent puff. The distortion of the velocity profile reduces the sudden change of the axial velocity across the rear of the turbulent puff. In numerical simulations, this proposal is reported to be successful in eliminating turbulence. Once having eliminated the turbulent puff, a forcing needed to distort the parabolic velocity profile may even be switched off, and the flow continues to re-laminarize. However, Hof et al. point out, that a distortion of the velocity profile at the turbulent laminar interface cannot be as readily implemented in practice as in simulations. Thus, they proposed to use a second turbulent puff upstream of the original one to distort the velocity profile at the rear end of the original puff. When the second turbulent puff is induced at a short distance upstream of the original puff, the short distance between the two puffs is insufficient to allow a parabolic velocity profile to fully develop, despite the fact that the flow is not turbulent between the two puffs. Hof et al. could show that introducing the additional puff allows for keeping the flow in a pipe laminar downstream of the additional puff, even in the area of the original puff. However, they pointed out that their simple strategy only works well for sufficiently small Reynolds-numbers of Re<2000 in pipes, Re<1400 in channels and Re<1800 in ducts, and that it becomes less efficient as Re increases, and once the regime of spatially expanding turbulence is reached (Re>2500 in pipes) it fails. On the other hand, in their numerical simulations, the basic concept of distorting the velocity profile to re-laminarize a turbulence proved successful even with larger Reynolds-numbers and reduced the drag more than by a factor of two.
There still remains a need of having a practicable method of and an apparatus for eliminating turbulence in wall bounded flows which also work at larger Reynolds-numbers.